/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.result.condition;

import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.server.ServerWebExchange;

/**
 * A logical conjunction (' && ') request condition that matches a request against
 * a set parameter expressions with syntax defined in {@link RequestMapping#params()}.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public final class ParamsRequestCondition extends AbstractRequestCondition<ParamsRequestCondition> {

    private final Set<ParamExpression> expressions;


    /**
     * Create a new instance from the given param expressions.
     *
     * @param params expressions with syntax defined in {@link RequestMapping#params()};
     * if 0, the condition will match to every request.
     */
    public ParamsRequestCondition(String... params) {
        this(parseExpressions(params));
    }

    private ParamsRequestCondition(Collection<ParamExpression> conditions) {
        this.expressions = Collections.unmodifiableSet(new LinkedHashSet<>(conditions));
    }


    private static Collection<ParamExpression> parseExpressions(String... params) {
        Set<ParamExpression> expressions = new LinkedHashSet<>();
        if (params != null) {
            for (String param : params) {
                expressions.add(new ParamExpression(param));
            }
        }
        return expressions;
    }


    /**
     * Return the contained request parameter expressions.
     */
    public Set<NameValueExpression<String>> getExpressions() {
        return new LinkedHashSet<>(this.expressions);
    }

    @Override
    protected Collection<ParamExpression> getContent() {
        return this.expressions;
    }

    @Override
    protected String getToStringInfix() {
        return " && ";
    }

    /**
     * Returns a new instance with the union of the param expressions
     * from "this" and the "other" instance.
     */
    @Override
    public ParamsRequestCondition combine(ParamsRequestCondition other) {
        Set<ParamExpression> set = new LinkedHashSet<>(this.expressions);
        set.addAll(other.expressions);
        return new ParamsRequestCondition(set);
    }

    /**
     * Returns "this" instance if the request matches all param expressions;
     * or {@code null} otherwise.
     */
    @Override
    public ParamsRequestCondition getMatchingCondition(ServerWebExchange exchange) {
        for (ParamExpression expression : expressions) {
            if (!expression.match(exchange)) {
                return null;
            }
        }
        return this;
    }

    /**
     * Returns:
     * <ul>
     * <li>0 if the two conditions have the same number of parameter expressions
     * <li>Less than 0 if "this" instance has more parameter expressions
     * <li>Greater than 0 if the "other" instance has more parameter expressions
     * </ul>
     * <p>It is assumed that both instances have been obtained via
     * {@link #getMatchingCondition(ServerWebExchange)} and each instance
     * contains the matching parameter expressions only or is otherwise empty.
     */
    @Override
    public int compareTo(ParamsRequestCondition other, ServerWebExchange exchange) {
        return (other.expressions.size() - this.expressions.size());
    }


    /**
     * Parses and matches a single param expression to a request.
     */
    static class ParamExpression extends AbstractNameValueExpression<String> {

        ParamExpression(String expression) {
            super(expression);
        }

        @Override
        protected boolean isCaseSensitiveName() {
            return true;
        }

        @Override
        protected String parseValue(String valueExpression) {
            return valueExpression;
        }

        @Override
        protected boolean matchName(ServerWebExchange exchange) {
            return exchange.getRequest().getQueryParams().containsKey(this.name);
        }

        @Override
        protected boolean matchValue(ServerWebExchange exchange) {
            return (this.value != null &&
                    this.value.equals(exchange.getRequest().getQueryParams().getFirst(this.name)));
        }
    }

}
